When you filet a Pacific saury, keep the backbone. You can also use the bone from salt-grilled Pacific saury.
Take all the flesh off the tail and bone. Wash the bone and tail well, and pat dry with paper towels. If there's any flesh left it will smell fishy, so remove it completely.
Cook the bones in a toaster oven for about 2 minutes. Don't let them burn too much.
Put the bones in hot sake and leave for a while. This works great with sake, but I recommend a stronger taste using shochu mixed with hot water - with a generous amount of shochu!
For Pacific saury bone crackers, see Recipe ID: 1570021
Story Behind this Recipe
Enjoy easy to make and delicious bone sake! Please see the Niconico Douga video (in Japanese, registration required) for this recipe: http://www.nicovideo.jp/watch/sm15572295
The most important point is to remove all the flesh from the bones beforehand. If there is any of the flesh remaining on the bones, it will smell fishy. My blog post for this recipe: http://ameblo.jp/cooking-s-papa/entry-11349601935.html